1. Field of the Invention
This invention relates to well tools and in particular, a well jar tool utilizing both rotational and radical displacement of latch components to initiate release of a latching member.
2. Description of the Prior Art
During drilling operations in certain situations or when encountering certain geological conditions, it sometimes occurs that devices, such as drill bits or other equipment related to drilling operations, connected within the drill string become engaged within the well bore and rotational axial movement of the drill string in either an advancing or retracting direction is prevented.
For this eventuality the prior art has disposed within the drill string a device known in the art as a well jar which serves to impart a substantial impactive force to the device engaged within the bore to effectuate the release thereof from its engaged position.
Several of the prior art jarring arrangements are operable in one axial direction only, thus necessitating the disposition in the drill string of two separate tools, one adapted for imposing a downward or "bumping" force on the engaged device, while the other is operable to impart an upward, or "jarring" force, on the engaged device. Of necessity such prior art devices require that a safety joint, or security device of some known type, be provided between the bumping and jarring tools. Despite the provision of such a joint, the possibility remains opens that disengagement of the adjacent tools could occur. Also, such tools deliver insufficient force to effectively disengage the engaged device and are, for these reasons, disadvantageous.
Other jars known in the art are able to alternatively transmit either a bumping or jarring force and eliminate the necessity of a safety joint by providing telescopically disposed inner and outer members normally latched in a neutral position and actuated by suitable tripping devices so as to bring surfaces thereon into impact-producing engagement upon release of the latching member. Typically, such jars utilize either exclusively rotational or radially outwardly displacement of the latching member to release the inner and outer members as the impact producing, or triggering, force is imposed thereupon. However, such jars are deficient in that the rotational or radially outwardly disengagement of the latching member requires gradual disengagement of the latching member from the member to which it is latched. As a corollary, as the force imposed on the latched member increases, the area of engaged contact between the latching and latched members necessarily decreases. Such a situation, whether in purely rotational or purely radially outwardly directed latching release, leads to the increased possibility of wear and premature failure of the latching member of prior art well jars.
It is therefore advantageous to provide a well jar which combines both rotational and radially outwardly movement of cooperatively arranged members so that the latching member is maintained in full engagement with a latched member of the jar until a full predetermined magnitude of the impact-producing force is imposed upon the jar. Thus, at only that instant does the disengagement of the latching member occur to thereby eliminate the wearing of parts resulting from gradual disengagement.
It is also advantageous to provide a well jar having a radially outwardly movable latching member and rotatably movable release member cooperating such that rotation of the release member places in registration an opening in the release member with the latching member. Thus, the simultaneous disengagement of the latching member and radially outwardly engagement of the latching member and the release member permits the parts of the jar to telescopically displace relative to the other to impact surfaces thereon to produce a disengaging impact. Further, it is advantageous to provide a well jar wherein rotation of the release member is occasioned by overlapped camming surfaces disposed both on the release member and an associated cam member in order to initiate rotation of the release member when a suitable force is transmitted thereinto so as to place in radial registration an opening in the release member with an extending portion disposed on the latching member. Of course, by overlapped, it is herein meant that the defined camming surfaces are engaged in a camming relationship along a camming interface.